1. Field of Invention
This invention relates to mobile communications devices and mobile computing devices. Specifically, the present invention relates to systems for providing backlighting to a keypad in a cellular flip telephone or personal digital assistant.
2. Description of the Related Art
Mobile communications devices are used in a variety of demanding applications ranging from hand-held global positioning system (GPS) devices to cellular telephones and personal digital assistants (PDAs). Such devices must often be lightweight, energy-efficient, durable, cost-effective, and user-friendly.
These features are particularly important in PDAs and cellular telephones. A PDA such as a Palm Pilot™ or other palm-top computer typically includes a processor running software such as Windows CE®, a keypad for user interface with the software, and a large liquid crystal display (LCD) screen mounted on a chassis or body. In many PDAs, the keypad is located on the inside surface of a lid often referred to as a ‘flip’. The flip is connected to the PDA body via a hinge mechanism so that when the flip is folded shut, the screen and the keypad are protected.
Typically, the hinge mechanism includes a flex circuit comprising flexible wire for routing signals across the hinge. Unfortunately, flex circuits readily fatigue and are difficult to route. This decreases the durability of the PDAs in which they are employed.
Often keypad backlighting is provided while the PDA receives user-input from the keypad. Typically, this requires a first flexible wire for providing power to several light emitting diodes (LEDs) in response to a control signal from a processor. The control signal is generated in response to user-input from the keypad. The processor reads user-input from the keypad via a second flexible wire. A third flexible wire provides a ground connection from the keypad to the PDA body. The use of three wires is inefficient and increases the probability of flex circuit fatigue.
Many PDA users also carry cellular telephones. Currently, to accommodate such users, many companies are integrating cellular telephones into their PDAs. To integrate a cellular telephone within a PDA, the PDA is typically equipped with a microphone, a cellular modem, a touch pad display screen, and a communications software package. When activated, the software displays a dialer interface on the touch pad screen that mimics the keypad on a typical cellular telephone. Unfortunately, activation of the software often requires extensive user knowledge and familiarity with the PDA and accompanying communications software package. As a result, such integrated devices are often not user friendly.
Hence, a need exists in the art for a user-friendly mechanism for making telephone calls with a PDA having an integrated cellular telephone. There exists a further need for a durable, cost effective, and space-efficient system and method to connect a keypad to its corresponding PDA body that can provide keypad backlighting and keypad reading functions over a single connection simultaneously.